It is known to provide a comparator with dual input stages, for example NMOS and PMOS input stages in the case of a CMOS comparator, in order to provide the comparator with a wide common-mode input voltage range. For example in such a comparator with supply voltages of 0 and Vdd the NMOS input stage may have a common mode input voltage range from about 1V to near Vdd and the PMOS input stage may have a common mode input voltage range from near 0 to about Vdd−1V, so that (for voltages Vdd of at least about 2V) the dual input stages together can have a common mode input voltage range from near 0 to near Vdd, i.e. the rail to rail voltage range.
In such a known comparator outputs of the dual input stages are summed and amplified in an analog form, for example using current summation, to constitute an overall analog comparator. Such a comparator may have a relatively complex circuit and may constitute all of an IC (integrated circuit) which is dedicated to the function of a comparator.
In mixed signal and other ICs that may be desired for specific applications, for example for power control, it may be desired to provide one or more comparators with a wide common-mode input voltage range, for example near rail to rail, without involving the complexity and die area of a dedicated comparator circuit.
There is a need to provide such a comparator.